Originally Posted by ograma
Thanks, good to know... But for all the other speakers, do you still want the physical distance -- distance being microphone to tweeter?
So in all my phase tweaking, I'm still not sure what phase setting to start with before running the Optimizer. Additionally, I have a variable phase control (0 to 180). I'm not sure how I would reverse the phase other than at the extremes.
Last, does anyone know if reversing the phase after the optimization should apply in all rooms?
I put this on the Sherwood R-972 User Thread. I hope you do not mind the repeat here.
No room EQ I have tested finds the phase of the subwoofer relative to the main channels. This requires test equipment to determine if the subwoofer phase is correct. A Radio Shack meter and the Stereophile Test Disc 1 should suffice. Use the warble tone on the test disc that comes closest to the subwoofer crossover. Set the volume to achieve a reading of roughly 80dB SPL (this number should swamp room noise, but not be so loud as to require hearing protection). Note the amplitude. Now reverse the phase of the subwoofer and see if the amplitude changes. Retain the setting that achieves the higher SPL.
The test must be done with any room EQ and is not an issue with the R-972. As an aside, the R-972 will correct any phase reversal with the main channel speakers unlike many room EQs.
To achieve optimal performance from a high-end system requires software that displays the response of your room at core listening positioning, especially in the presence of a subwoofer. I use AcoustiSoft RPlusD, which reports the Radio Shack SPL meter can be used as a microphone (OK below 500Hz). There is a calibration file for the Radio Shack meter on the AcoustiSoft site. RPlusD does have a learning curve, but AcoustiSoft's on-line documentation is a great reference. Click on the link Introducing RPlusD Modal Analyzer at the top of the home page. Other, less intensive, test systems may be available. I do not have experience with them. The simpler ones may not allow multiple measurements averaging or may do it incorrectly.